In the field of face authentication or cosmetic surgery, three-dimensional shape measurement of a face is highly demanded. In such a field, it is not preferred to direct intense light toward eyes and movement of a face is likely during measurement. Therefore, a passive method such as a stereo method is more suitable than an active method such as scanning with laser beams or the like.
A stereo correspondence search algorithm using phase-only correlation (POC) (an algorithm bringing identical points in images consisting of a base image and a reference image, each of which is a stereo image, into correspondence with each other) has attracted attention in terms of its robustness and high accuracy.
Patent Document 1 below discloses a through hole measurement system applying the phase-only correlation method to a stereo camera.
Non-Patent Document 1 below discloses a window size and noise influence in a POC operation.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-010392    Non-Patent Document 1: “Improving Performance for Subpixel Image Matching Based on Phase-Only Correlation,” The Society of Instrument and Control Engineers Tohoku Chapter, 218th Workshop, Oct. 9, 2004, material number 218-15